Ground-state α-decay of N = 128 isotones 216Ra, 217Ac and 218Th

The α-decay properties of very short-lived N = 128 isotones, ²¹⁶Ra, ²¹⁷Ac and ²¹⁸Th, were investigated by the pulsed-beam method. Alpha emitters of interest were produced in the bombardment of ²⁰⁸Pb or ²⁰⁹Bi with 65–96 MeV ¹²C or ¹⁴N ions and α-decays were measured between natural beam bursts of the cyclotron. The results obtained are _Eα = 9.349±0.008 MeVand $\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 182±10}\text{ns for}{}^{216}\text{Ra}\text{, 9.650±0.010}\text{MeV}$ and $\text{111±7}\text{ns for}{}^{217}\text{Ac}\text{, 9.665±0.010}\text{MeV}$ and $\text{96±7}\text{ns for}{}^{218}\text{Th}$. The experimental reduced α-widths of N = 128 isotones from ²¹²Po to ²¹⁸Th are shown to agree well with the simple shell model calculation.     

Penetration of ammonia molecule into ice film; activation energy analysis using Xe molecular beam irradiation

We have investigated the barrier energy for an ammonia molecule to penetrate into ice film by the use of infrared spectroscopy and Xe supersonic beam. After the ice film on a Pt(1 1 1) surface is exposed to ammonia molecules, an umbrella mode of ammonia molecules adsorbed on the ice film has been observed in infrared spectra. After the irradiation of accelerated Xe beam, we observed an energy shift of the mode of ammonia. The shifted mode is assigned to that of ammonia molecules at the interface between the ice film and the Pt(1 1 1) surface. This indicates that the collision with Xe beam induced the penetration of an ammonia molecule to the interface through the ice film. Using this feature, we estimate a barrier for penetration as 0.28 ± 0.03 eV which is much smaller than the one previously reported for bulk ice.     

Collinear fast atomic-beam laser spectroscopy at riken garis/igisol

We have constructed a fast atomic-beam collinear laser spectroscopy system connected to the on-line isotope separator facility GARIS/IGISOL at RIKEN. This system is potentially powerful in studying refractory elements. To test the system, an off-line collinear experiment was made on stable Hf isotopes produced by means of laser ablation technique. For production of radioactive Hf isotopes, the use of the inverse kinematics of a fusion reaction,⁹Be(¹⁶⁶Er,xn)^175-x Hf, was investigated. The radioactive isotope¹⁶⁹Hf was successfully extracted from GARIS/IGISOL and accelerated up to 30 keV.     

Structural studies of phase transitions in crystalline and liquid halides (ZnCl<Subscript>2</Subscript>, AlCl<Subscript>3</Subscript>) under pressure

The results of investigating the phase diagrams of ZnCl₂ and AlCl₃ halides, as well as the structure of the shortrange order of the corresponding melts under pressures up to 6.5 GPa, by the method of energy-dispersive x-ray diffraction are reported. When a ZnCl₂ crystal is compressed, a phase transition occurs from the γ phase (HgI₂ structure type) to the δ phase (distorted CdI₂ structure, WTe₂ type). The structural studies of the liquid state of ZnCl₂ and AlCl₃ indicate that the intermediate-range order decreases rapidly in the tetrahedral network of both melts as the pressure increases to 1.8 and 2.3 GPa for ZnCl₂ and AlCl₃, respectively. With further compression, the transitions in both melts occur with a change in the structure of the short-range order and with an increase in the coordination number. In this case, the transition in AlCl₃ occurs at ≈4 GPa and is a sharp first order transition, whereas the transition in ZnCl₂ occurs more smoothly in a pressure range of 2–4 GPa with a maximum intensity near 3 GPa. Thus, the AlCl₃ and ZnCl₂ compounds exemplify the existence of two phenomena—gradual decay of intermediate-range structural correlations and a sharper liquid-liquid coordination transition.     

Preequilibrium α-particle emission in heavy-ion reactions

The α-particle emission following ¹⁴N-induced reactions on various heavy targets at 85–115 MeV has been studied. Cross sections of heavy residual nuclei produced after α-emission were measured in the case of the ²⁰⁹Bi target and were found to be close to the angle-integrated cross sections of α-particles, indicating that the α-emission mainly takes place in a binary process. The measured angular distributions of α-particles are pronouncedly forward-peaked, while the energy spectra are always characterized by the Maxwellian distribution even at forward angles and reproduced excellently by the statistical evaporation formula when nuclear temperature is treated as a free parameter. The resultant value of the temperature is high (4–6 MeV) at forward angles and decreases monotonically with increasing emission angles.The energy and angular distributions of protons, deuterons and tritons were also measured in the ¹⁸¹Ta + ¹⁴N reaction at 115 MeV. The results are similar to those of α-particles. In particular, nuclear temperatures turned out nearly equal to each other, being consistent with the hot-spot interpretation for the relevant preequilibrium light-particle emission.     

Gamma-rays from an incomplete fusion reaction induced by 95 MeV 14N

Gamma-rays from the ${}^{159}\text{Tb}\text{(}{}^{14}\text{N}\text{, αx}\text{n}\text{)}{}^{\mathrm{169?x}}\text{Yb}$ reaction, in which non-evaporation α-particles are emitted, have been identified. Yields of E2 cascade transitions suggest that the angular momentum distribution of the entrance channel leading to this reaction is localized just above the critical angular momentum for complete fusion.     

Dielectric elastomer switches for smart artificial muscles

Some of the most exciting possibilities for dielectric elastomer artificial muscles consist of biologically inspired networks of smart actuators working towards common goals. However, the creation of these networks will only be realised once intelligence and feedback can be fully distributed throughout an artificial muscle device. Here we show that dielectric elastomer artificial muscles can be built with intrinsic sensor, control, and driver circuitry, bringing them closer in capability to their natural analogues. This was achieved by exploiting the piezoresistive behaviour of the actuator’s highly compliant electrodes using what we have called the dielectric elastomer switch. We developed suitable switching material using carbon loaded silicone grease and experimentally demonstrated the primitives required for self-sensing actuators and digital computation, namely compliant electromechanical NAND gates and oscillator circuits. We anticipate that dielectric elastomer switches will reduce the need for bulky and rigid external circuitry as well as provide the simple distributed intelligence required for soft, biologically inspired networks of actuators. Examples include many-degree-of-freedom robotic hearts, intestines, and manipulators; wearable assistive devices; smart sensor skins and fabrics; and ultimately new types of artificial muscle embedded, electromechanical computers.     

Universal dynamics behavior in superionic conducting glasses

The inelastic neutron scattering experiment on superionic glass system AgI-AgPO₃ have been performed in the energy and momentum transfer range from ? 5 to 15 meV and 0 to 8 Å^? 1, respectively by using a time of flight MARI instrument at Rutherford Appleton Laboratory, ISIS, UK. The E-dependence of the inelastic data show an excess intensity at low energy around 3 meV, the so-called Boson peak, which increased with the dopant salt. The Q-dependence of the elastic scattering reveals a prepeak at anomalously low Q value around 0.8 Å^? 1, which is not observed in the undoped AgPO₃ glass. The Q-dependence in the energy region from 1 to 3 meV shows clearly an excess intensity at Q ~ 2.2 Å ^? 1compared with the undoped AgPO₃. All these features correlate with the increasing mobility of Ag⁺ ions due to the expansion of the network structure caused by salt doping, which leads to the increase of ionic conductivity. Similar results have also been observed in the corresponding superionic glass system AgI-Ag₂S-AgPO₃ that was observed by both MARI and NEAT instrument at HMI, Berlin. The results show a universal dynamic behavior in silver phosphate glasses.     

Mössbauer spectra and electrical conductivity ofxFe2O3−(40-x)V2O5−60P2O5 glasses

Mössbauer spectra and electrical conductivities were measured for the purpose of studying on the conduction mechanism of xFe₂O₃?(40-x)V₂O₅?60P₂O₅ glasses. The ratios Fe²⁺/Fe²⁺+Fe³⁺ in xFe₂O₃?(40-x)V₂O₅?60P₂O₅ glasses were determined by Mössbauer spectroscopy. On the composition dependence of D. C. conductivities in these glasses, the minimum of log σ at each temperature was obtained at 25Fe₂O₃?15V₂O₅?60P₂O₅. The conductivities of ternary glassses in Fe rich region could be explained only by the changes of carrler (Fe²⁺) concentration and the hopping conduction between Fe²⁺ ions and Fe³⁺ ions in binary glasses. In V rich region, the saturation tendency of D. C. conductivities are observed. It was suggested to be explained by increasing of V⁴⁺ ions due to the influence of Fe ions.     

Application of the Mössbauer spectroscopy to the study of the oxidation state of azaferrocene derivatives

Azaferrocene has two active sites of iron and nitrogen atoms. Drastic change of the oxidation state in iodine oxidation of azaferrocene is observed by introducing the methyl substituents into the pyrrole ring, while all the N-methylates show a similar electronic state. It was revealed that an introduction of methyl substituent to the pyrrole ring promotes the oxidation of nitrogen atom in pyrrole ring more than the central iron atom.